JP4748445B2 - Cutting tool made of super-high-pressure sintered material with surface-coated cubic boron nitride that exhibits excellent chipping resistance with a hard coating layer in intermittent cutting of high-hardness steel - Google Patents

Description

  In the present invention, the hard coating layer has excellent heat resistance and high temperature hardness, and further excellent high temperature strength and impact resistance strength. Therefore, the high hardness steel such as a hardened material of alloy steel and bearing steel can be obtained. Surface-coated cubic with a hard coating layer formed on the surface of a cutting tool base made of cubic boron nitride based ultra-high pressure sintered material that exhibits excellent chipping resistance even when used in high-speed intermittent cutting The present invention relates to a cutting tool made of a crystalline boron nitride-based ultrahigh pressure sintered material (hereinafter referred to as a coated cBN-based sintered tool).

  In general, a coated cBN-based sintered tool can be attached to a throwaway tip that is detachably attached to the tip of a cutting tool for turning various work materials such as steel and cast iron, and the throwaway tip can be detachably attached. There are known slow-away end mills that are attached and cut in the same manner as solid type end mills used for chamfering, grooving, and shoulder machining.

  In addition, as a coated cBN-based sintered tool, Ti nitride (TiN) is formed on the surface of a tool body made of various cubic boron nitride-based ultrahigh pressure sintered materials (hereinafter referred to as cBN-based sintered materials). A coated cBN-based sintered tool is known in which a surface coating layer such as a layer, a Ti / Al composite nitride layer, a Cr / Si composite nitride layer, or a Ti / Cr / Si composite nitride layer is deposited. It is also known that these are used for cutting various steels and cast irons, for example.

Further, the above-mentioned coated cBN-based sintered tool is loaded with the above-mentioned tool base in an arc ion plating apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG. For example, a cathode electrode (evaporation source) made of metal Ti, a Ti—Al alloy, a Cr—Si alloy, a Ti—Cr—Si alloy, etc. each having a predetermined composition in a state heated to 500 ° C., and an anode electrode During this time, for example, a current of 90 A is applied to generate arc discharge, and at the same time, nitrogen gas is introduced into the apparatus as a reaction gas to obtain a reaction atmosphere of, for example, 2 Pa, while the tool base has, for example, −100 V On the surface of the tool base, a desired voltage such as a TiN layer, a (Ti, Al) N layer, a (Cr, Si) N layer, or a (Ti, Cr, Si) N layer is applied on the surface of the tool base. It is also known to be produced by depositing a layer of minute composition.
JP-A-7-300649

In recent years, FA has been remarkable for cutting devices, but on the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and accordingly, cutting is performed at higher speed conditions in addition to normal cutting conditions. Although there is a tendency to require lower cutting, the above-described conventional coated tool does not cause any particular problem when various types of steel and cast iron are cut under normal conditions. However, when this is used for high-speed intermittent cutting of high-hardness steel having a Vickers hardness (C scale) of 50 or more, such as a hardened material of alloy steel or bearing steel, Mechanical thermal shock is applied at a very fast pitch. On the other hand, the (Ti, Cr, Si) N layer that forms the upper layer of the hard coating layer does not have sufficient high-temperature strength and impact resistance. (Slight chipping) occurs, and as a result, the service life is reached in a relatively short time.

Therefore, the present inventors, from the above viewpoint, coated cBN exhibiting excellent chipping resistance with a hard coating layer particularly in high-speed intermittent cutting of hardened steel such as alloy steel and hardened material of bearing steel. As a result of research to develop a basic sintered tool,
(a) a composite nitride of Ti, Cr, and Si constituting the hard layer _{([Ti 1-X-Y} Cr X Si Y] N) layer, the value of the content X (atomic ratio) of Cr is 0 0.03 to 0.30, and the content ratio Y (atomic ratio) of Si is within a range of 0.01 to 0.05, and has predetermined heat resistance, high temperature hardness, and high temperature strength. Although it has the wear resistance required under certain conditions, in high-speed intermittent cutting of high-hardness steel where mechanical thermal shock is applied to the cutting edge at an extremely fast pitch, a composite of Ti, Cr and Si is used. nitride _{([Ti 1-X-Y} Cr X Si Y] N) hard coating layer consisting of layer high-temperature strength, in order to insufficient impact strength, that chipping tends to occur.

(B) On the other hand, the Ti nitride (TiN) layer has excellent high-temperature strength and impact strength, but it cannot be said to have sufficient heat resistance and high-temperature hardness. In high-speed intermittent cutting of high-hardness steel subjected to impact, it cannot be said that even if the hard coating layer is composed only of a Ti nitride (TiN) layer, it has sufficient wear resistance.

(C) The above-mentioned (a) Cr content ratio X is 3 to 30 atomic% and Si content ratio Y is 1 to 5 atomic%, which has predetermined heat resistance, high temperature hardness and high temperature strength [Ti _{1-X -Y} Cr _X Si _Y] N (provided that each atomic ratio, X is 0.03 to 0.30, Y 0.01 to 0.05) layer (hereinafter, referred to as thin layer a), the laminate While heat resistance and high-temperature hardness are inferior to A, Ti nitride (TiN) layers (hereinafter referred to as thin layers B) having excellent high-temperature strength and impact strength are averaged over each layer. When the upper layer of the hard coating layer is formed by alternately laminating the layers with a thickness of 0.01 to 0.3 μm, the hard coating layer of this alternate laminated structure has the excellent heat resistance of the thin layer A. In addition to having high temperature hardness, it has both high temperature strength and impact strength superior to those of thin layer B. To become so that.
The research results shown in (a) to (c) above were obtained.

This invention was made based on the above research results,
In the surface-coated cubic boron nitride-based ultra-high pressure sintered material cutting tool in which a hard coating layer is vapor-deposited on the surface of the insert made of ultra-high pressure sintered material containing 30 to 95% by mass of boron nitride,
(A) The hard coating layer consists of a lower layer having an average layer thickness of 1.5 to 6 μm and an upper layer having an average layer thickness of 0.3 to 3 μm,
(B) The lower layer of the hard coating layer was formed by vapor deposition.
_{Formula: [Ti 1-X-Y} Cr X Si Y] N ( provided that both atomic ratio, X is 0.03 to 0.30, Y represents a 0.01-0.05) satisfies A composite nitride layer of Ti, Cr and Si;
(C) The upper layer of the hard coating layer is formed by vapor deposition on the surface of the lower layer, and each has an alternately laminated structure of thin layers A and B each having an average layer thickness of 0.01 to 0.3 μm. And
The thin layer A is
_{Formula: [Ti 1-X-Y} Cr X Si Y] N ( provided that both atomic ratio, X is 0.03 to 0.30, Y represents a 0.01-0.05) satisfies A composite nitride layer of Ti, Cr and Si;
The thin layer B is a Ti nitride (TiN) layer,
Surface-coated cubic boron nitride-based ultra-high pressure sintered material cutting tool that exhibits excellent chipping resistance in high-speed intermittent cutting of high-hardness steel, formed by vapor-depositing a hard coating layer consisting of It is characterized by a coated cBN-based sintered tool).

Next, the reason why the hard coating layer of the coated cBN-based sintered tool of the present invention is numerically limited as described above will be described.
(A) Content of boron nitride (cBN) When the boron nitride (cBN) content in the insert made of ultrahigh pressure sintered material is less than 30% by mass, the hardness of the cBN sintered material is reduced, and the ultrahigh pressure is increased. When performing high-hardness intermittent cutting using a sintered material insert, it is impossible to provide the minimum required hardness, wear resistance is reduced, and boron nitride (cBN) content Is more than 95% by mass, it becomes difficult to ensure the adhesion strength between the cBN sintered material and the hard coating layer, and as a result, the hard coating layer is easily peeled off. Therefore, in this invention, the boron nitride (cBN) content Was determined to be 30 to 95% by mass.

(B) a composite nitride of Ti, Cr, and Si constituting the hard layer lower layer constituting the lower layer Ti component in _{([Ti 1-X-Y} Cr X Si Y] N) layer holds the heat resistance, Since the Cr component contributes to maintaining the high temperature strength and the Si component contributes to the improvement of the high temperature hardness, the composite nitride of Ti, Cr and Si constituting the lower layer of the hard coating layer ([Ti _{1-X- Y} Cr X _{Si Y] N)} layer has a predetermined heat resistance, a layer having a high-temperature strength and high-temperature hardness, ensuring the wear resistance of the cutting edge during high-speed intermittent cutting work of hardened steels Basically play a role. However, although the high temperature strength of the lower layer is improved when the Cr content ratio X exceeds 30 atomic%, the heat resistance is reduced due to the relative decrease in the Ti content ratio, while the Cr content ratio X is 3 atoms. If it is less than%, the high-temperature strength is reduced and chipping is likely to occur. On the other hand, if the Si content ratio Y exceeds 5 atomic%, the high temperature hardness of the lower layer is increased and the wear resistance is improved, but the heat resistance is reduced due to the relative decrease in the Ti content ratio. When the Si content Y is less than 1 atomic%, the high-temperature hardness decreases, and the progress of wear of the cutting edge during high-speed interrupted cutting is rapidly accelerated, so that sufficient wear resistance can be secured. Since it disappeared, the value of Si content ratio Y was determined to be 0.01 to 0.05.
Moreover, if the average layer thickness of the lower layer is less than 1.5 μm, the heat resistance, high temperature hardness and high temperature strength possessed by itself cannot be imparted to the hard coating layer over a long period of time, resulting in a short tool life. When the layer thickness exceeds 6 μm, chipping is likely to occur. Therefore, the average layer thickness is set to 1.5 to 6 μm.
Note that a thin layer of titanium nitride (TiN) can be interposed between the base and the lower layer in order to ensure sufficient adhesion between the insert base made of the ultra-high pressure sintered material and the lower layer. The thin layer of TiN has little effect of improving the adhesion when the layer thickness is less than 0.01 μm, and on the other hand, even if the layer thickness exceeds 0.5 μm, further improvement in adhesion cannot be expected. The thickness of the TiN layer interposed between the substrate and the lower layer is preferably 0.01 μm or more and 0.5 μm or less.

(C) Upper layer thin layer A
Composite nitride of Ti, Cr, and Si constituting a thin layer A of the upper layer _{([Ti 1-X-Y} Cr X Si Y] N) layer (where each atomic ratio, X is from 0.03 to 0. 30 and Y are 0.01 to 0.05), which is substantially the same layer as the lower layer, and has predetermined heat resistance, high temperature hardness and high temperature strength, and high-speed intermittent cutting of high hardness steel. It has the effect | action which ensures the abrasion resistance of the cutting blade part at the time.

(D) Upper layer thin layer B
The thin layer B composed of the Ti nitride (TiN) layer is an upper layer composed of the alternately laminated structure of the thin layer A and the thin layer B. In other words, characteristics that the thin layer A lacks (high temperature strength, impact strength) The main purpose is to compensate.
As described above, the thin layer A as the upper layer is a layer having predetermined heat resistance, high temperature hardness and high temperature strength, but in high-speed intermittent cutting of high hardness steel to which mechanical thermal shock is applied at a fast pitch. The high temperature strength and impact strength are not sufficient.
Therefore, the thin layer B composed of the Ti nitride (TiN) layer having excellent high-temperature strength and impact strength is arranged alternately with the thin layer A to form an alternate laminated structure, thereby forming the adjacent thin layer A. Compensating for the lack of high-temperature strength, the upper layer as a whole has superior heat resistance and impact strength that are superior to those of the thin layer B, without damaging the high-temperature hardness of the thin layer A. Forming an upper layer.
The Ti nitride (TiN) layer has excellent high-temperature altitude and impact strength, and has an action of preventing the occurrence of pitting in high-speed intermittent cutting of high-hardness steel to which mechanical thermal shock is applied at a high pitch.

(E) Upper layer thin layer A and thin layer B one layer average layer thickness, upper layer average layer thickness Upper layer thin layer A and thin layer B, each layer average layer thickness is less than 0.01 μm, respectively The excellent properties of the thin layer cannot be demonstrated, and as a result, it is impossible to ensure the superior heat resistance, high temperature hardness, higher temperature strength, and impact resistance strength of the upper layer. If the average layer thickness of the layer exceeds 0.3 μm, the disadvantages of each thin layer, that is, if the thin layer A is insufficient in high temperature strength and impact strength, if the thin layer B is in heat resistance, high temperature hardness The shortage appears locally in the layer, which causes chipping and rapid wear. Therefore, the average layer thickness of each layer is determined to be 0.01 to 0.3 μm. It was.
That is, the thin layer B is provided in order to give a higher temperature strength and impact strength superior to the upper layer, but the average layer thickness of each of the thin layer A and the thin layer B is 0.01 to If it is within the range of 0.3 μm, the upper layer composed of the alternately laminated structure of the thin layer A and the thin layer B has excellent heat resistance and high temperature hardness, and further improved high temperature strength and impact resistance strength. It acts as if it is a single layer, but when the average layer thickness of each of the thin layers A and B exceeds 0.3 μm, the high temperature strength of the thin layer A, the impact strength is insufficient, or The heat resistance of the thin layer B and the lack of high-temperature hardness appear locally in the layer, and the upper layer cannot exhibit good characteristics as a single layer as a whole. The average layer thickness of each layer B was determined to be 0.01 to 0.3 μm.
Excellent heat resistance and high temperature hardness by forming on the lower layer surface an upper layer composed of an alternating laminated structure in which the average layer thickness of the thin layers A and B is in the range of 0.01 to 0.3 μm. At the same time, it is possible to obtain a hard coating layer having both higher temperature strength and impact resistance strength.
In addition, when the total average layer thickness of the upper layer (that is, the total layer thickness of the thin layers A and B constituting the alternate laminated structure) is less than 0.3 μm, the high-speed steel has a high speed. Sufficient heat resistance, high temperature hardness, high temperature strength and impact strength required for interrupted cutting cannot be imparted to the upper layer, resulting in a short tool life, while the average layer thickness is 3 μm. If it exceeds, chipping is likely to occur, so the average layer thickness was determined to be 0.3 to 3 μm.

In the coated cBN-based sintered tool of the present invention, a slightly different interference color may be generated depending on the thickness of the coating layer on the outermost surface, and the tool appearance may be uneven. In such a case, unevenness of the appearance of the tool can be prevented by thickly depositing a Ti nitride (TiN) layer or a Ti / Si composite nitride (TiSiN) layer on the outermost surface. At that time, if the average layer thickness of the TiN layer or TiSiN layer is less than 0.2 μm, uneven appearance cannot be prevented, and if the average layer thickness is up to 2 μm, uneven appearance can be sufficiently prevented. The average layer thickness of the nitride (TiN) layer or the composite nitride of Ti and Si (TiSiN) layer may be 0.2 to 2 μm.
In addition, the surface roughness of the coated cBN-based sintered tool base of the present invention is desirably 0.05 to 1.0 in terms of Ra. If the surface roughness Ra is 0.05 or more, an improvement in adhesion strength between the substrate and the hard coating layer due to the anchor effect can be expected. On the other hand, if Ra exceeds 1.0, the finished surface of the work material This is because the accuracy is adversely affected.

  In the coated cBN-based sintered tool of the present invention, the hard coating layer is composed of an upper layer and a lower layer, and the upper layer of the hard coating layer has excellent heat resistance by having an alternating laminated structure of thin layers A and thin layers B. High-temperature hardness, high-temperature strength and impact strength combined, so high-speed mechanical mechanical shock is applied to the cutting edge of extremely hard steel such as alloy steel and bearing steel hardened materials at an extremely fast pitch. Even in the cutting under severe conditions such as intermittent cutting, the hard coating layer exhibits excellent wear resistance over a long period of time without occurrence of chipping.

  Next, the coated cBN-based sintered tool of the present invention will be specifically described with reference to examples.

As raw material powders, cubic boron nitride (cBN) powder, titanium carbide (TiC) powder, titanium nitride (TiN) powder, titanium carbonitride (TiCN) powder each having an average particle size in the range of 0.5 to 4 μm , Tungsten carbide (WC) powder, Al powder, Co powder, Ti ₃ Al powder that is an intermetallic compound powder of Ti and Al, TiAl powder, and TiAl ₃ powder, and a composite metal nitride having a composition formula: Ti ₂ AlN Prepare powder, TiB ₂ powder, aluminum nitride (AlN) powder, aluminum boride (AlB ₂ ) powder, aluminum oxide (Al ₂ O ₃ ) powder, and blend these raw material powders into the composition shown in Table 1, After wet mixing with a ball mill for 80 hours and drying, a green compact having a diameter of 50 mm × thickness of 1.5 mm was preliminarily formed at a pressure of 120 MPa. Then, the green compact is sintered in a vacuum atmosphere at a pressure of 1 Pa at a predetermined temperature within a range of 900 to 1300 ° C. for 60 minutes to obtain a presintered body for a cutting blade piece. This pre-sintered body is overlaid with a separately prepared WC-based cemented carbide support piece having dimensions of Co: 8% by mass, WC: remaining composition, and diameter: 50 mm × thickness: 2 mm. In an ordinary ultra high pressure sintering apparatus, the normal pressure is 5 GPa, the temperature is 1200 ° C. within a predetermined temperature range of 1200 to 1400 ° C., and the holding time is 0.8 hours. After sintering, the upper and lower surfaces are polished with a diamond grindstone and divided into a regular triangle shape with a side of 3 mm by a wire electric discharge machine, and Co: 5% by mass, TaC: 5% by mass, WC: remaining composition And CIS standard SNGA12041 shape (thickness: 4 In the brazed part (corner part) of the WC-based cemented carbide chip body having a 76 mm × one side length: 12.7 mm regular triangle), by mass%, Cu: 30%, Zn: 28%, Ni: After brazing using a brazing material of Ag alloy having a composition of 2%, Ag: remaining, and processing the outer periphery to a predetermined dimension, the cutting edge is subjected to a honing process of width: 0.15 mm, angle: 25 ° Further, by performing finish polishing, tool bases A to J each having a chip shape of ISO standard SNGA12041 were manufactured.

(A) Next, each of the tool bases A to J is ultrasonically cleaned in acetone and dried, and then in a radial direction from the central axis on the rotary table in the arc ion plating apparatus shown in FIG. Are mounted along the outer periphery at a predetermined distance, and the upper layer thin layer B forming metal Ti is used as the cathode electrode (evaporation source) on one side, and the cathode electrode (evaporation source) on the other side. The upper layer thin layer A and the lower layer forming Ti—Cr—Si alloy each having a component composition corresponding to the target composition shown in Table 2 are arranged opposite to each other with the rotary table interposed therebetween,
(B) First, while the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, the inside of the apparatus is heated to 500 ° C. with a heater, and then Ar gas is introduced to create an atmosphere of 0.7 Pa. A DC bias voltage of −200 V is applied to the tool base that rotates while rotating on the table, and the tool base surface is bombarded with argon ions.
(C) Nitrogen gas is introduced as a reaction gas into the apparatus to form a reaction atmosphere of 3 Pa, a DC bias voltage of −100 V is applied to the tool base rotating while rotating on the rotary table, and the thin layer A current of 100 A is passed between A and the lower layer forming Ti—Cr—Si alloy and the anode electrode to generate an arc discharge, and the target composition and target layer thickness shown in Table 2 are formed on the surface of the tool base. The (Ti, Cr, Si) N layer is deposited as a lower layer of the hard coating layer,
(D) Next, the flow rate of nitrogen gas as a reaction gas introduced into the apparatus is adjusted to obtain a reaction atmosphere of 2 Pa, and within a range of −10 to −100 V on the tool base that rotates while rotating on the rotary table. In a state where a predetermined DC bias voltage is applied, a predetermined current within a range of 50 to 200 A is passed between the cathode electrode and the anode electrode of the thin layer B forming metal Ti to generate arc discharge, A thin layer B having a predetermined layer thickness is formed on the surface of the tool base, and after the thin layer B is formed, the arc discharge is stopped. Instead, the cathode of the thin layer A and the lower layer forming Ti—Cr—Si alloy is formed. Similarly, a predetermined current in the range of 50 to 200 A is passed between the electrode and the anode electrode to generate arc discharge to form a thin layer A having a predetermined layer thickness. Then, the arc discharge is stopped and the thin layer B is again formed. Forming metal Ti The formation of the thin layer B by arc discharge between the sword electrode and the anode electrode and the formation of the thin layer A by arc discharge between the cathode electrode and the anode electrode of the thin layer A and the lower layer forming Ti—Cr—Si alloy are alternately performed. Table 2 shows the upper layer composed of the alternate lamination of the thin layer A and the thin layer B having the target composition and the single target layer thickness along the layer thickness direction on the surface of the tool base. The present invention-coated cBN-based sintered tools 1 to 9 were produced by vapor deposition with the total layer thickness (average layer thickness) shown.

  For comparison purposes, each of the tool bases A to J described above is ultrasonically cleaned in acetone and dried, and then charged into a normal arc ion plating apparatus shown in FIG. As the (evaporation source), a Ti—Cr—Si alloy having a component composition corresponding to the target composition shown in Table 3 is mounted, and the apparatus is first evacuated and kept at a vacuum of 0.1 Pa or less. After heating the interior of the apparatus to 500 ° C. with a heater, Ar gas was introduced to create an atmosphere of 0.7 Pa, and a DC bias voltage of −200 V was applied to the tool base rotating while rotating on the table. Then, the surface of the tool base is bombarded with argon ions, and then nitrogen gas is introduced into the apparatus as a reaction gas to make a reaction atmosphere of 3 Pa and applied to the tool base. The bias voltage is lowered to −100 V to generate an arc discharge between the cathode electrode and the anode electrode of the Ti—Cr—Si alloy, and the surface of each of the tool bases A to J is shown in Table 3. Conventionally coated cBN-based sintered tools 1 to 9 were manufactured by vapor-depositing a hard coating layer composed of a (Ti, Cr, Si) N layer having a target composition and a target layer thickness.

Next, according to the present invention, the coated cBN-based sintered tools 1 to 9 and the conventional coated cBN-based sintered tools, in a state where all of the above-mentioned coated cBN-based sintered tools are screwed to the tip of the tool steel tool with a fixing jig. For cBN-based sintered tools 1-9,

Work material: JIS · SCM415 (hardness: HRC61) lengthwise equidistant four round grooved round bars,
Cutting speed: 180 m / min. ,
Cutting depth: 0.12 mm,
Feed: 0.12 mm / rev. ,
Cutting time: 5 minutes,
Dry interrupted high-speed cutting test of alloy steel under the conditions (referred to as cutting condition A) (normal cutting speed is 120 m / min.),
Work material: JIS / SUJ2 (Hardness: HRC62) lengthwise equidistant round bars with 8 vertical grooves,
Cutting speed: 200 m / min. ,
Cutting depth: 0.15 mm,
Feed: 0.15 mm / rev. ,
Cutting time: 5 minutes,
Dry intermittent high-speed cutting test of the bearing steel under the conditions (referred to as cutting condition B) (normal cutting speed is 150 m / min.),
Work material: JIS · SKD61 (Hardness: HRC63) lengthwise equally spaced 8 rods with vertical grooves,
Cutting speed: 150 m / min. ,
Cutting depth: 0.15 mm,
Feed: 0.10 mm / rev. ,
Cutting time: 5 minutes,
A dry interrupted high-speed cutting test of a die steel under the conditions (referred to as cutting condition C) (normal cutting speed is 100 m / min.),
In each cutting test, the flank wear width of the cutting edge was measured. The measurement results are shown in Table 4.

  As a result, the composition of the hard coating layers of the present coated cBN-based sintered tools 1 to 9 and the conventional coated cBN-based sintered tools 1 to 9 are analyzed by energy dispersive X-ray analysis using a transmission electron microscope. As a result of measurement, each showed substantially the same composition as the target composition.

  Further, when the average layer thickness of the constituent layers of the hard coating layer was subjected to cross-sectional measurement using a transmission electron microscope, all showed the same average value (average value of five locations) as the target layer thickness.

  From the results shown in Tables 2 to 4, all of the coated cBN-based sintered tools of the present invention have a hard coating layer, and alternate layers of thin layer A and thin layer B each having an average layer thickness of 0.01 to 0.3 μm. It consists of an upper layer having an average layer thickness (total layer thickness) of 0.3 to 3 μm and a lower layer having an average layer thickness of 1.5 to 6 μm, and the lower layer has excellent heat resistance and high temperature strength. It has excellent high temperature hardness, and the upper layer has excellent heat resistance, high temperature hardness and superior high temperature strength and impact resistance. Even in high-speed intermittent cutting of high-hardness steel, excellent wear resistance is exhibited without occurrence of chipping, whereas the hard coating layer is a conventional coated cBN base composed of a single (Ti, Cr, Si) N layer. Sintered tools are particularly difficult due to lack of high temperature strength and impact strength of the hard coating layer. Since ping occurs, it is clear that lead to a relatively short time service life.

  As described above, the coated cBN-based sintered tool of the present invention is not only used for cutting under normal cutting conditions such as various types of steel and cast iron, but particularly as high as a hardened material for alloy steel and bearing steel. Even in severe cutting conditions such as high-speed interrupted cutting of hardened steel, where mechanical thermal shock is applied to the cutting edge at an extremely fast pitch, the hard coating layer has excellent wear resistance without chipping. Since it is demonstrated over a long period of time, it can sufficiently satisfy the high performance of the cutting device, the labor saving and energy saving of the cutting, and the cost reduction.

The arc ion plating apparatus used for forming the hard coating layer which comprises the coated cBN group sintered tool of this invention is shown, (a) is a schematic plan view, (b) is a schematic front view. It is a schematic explanatory drawing of a normal arc ion plating apparatus.

Claims (1)

In the surface-coated cubic boron nitride-based ultra-high pressure sintered material cutting tool in which a hard coating layer is vapor-deposited on the surface of the insert made of ultra-high pressure sintered material containing 30 to 95% by mass of boron nitride,
(A) The hard coating layer consists of a lower layer having an average layer thickness of 1.5 to 6 μm and an upper layer having an average layer thickness of 0.3 to 3 μm,
(B) The lower layer of the hard coating layer was formed by vapor deposition.
_{Formula: [Ti 1-X-Y} Cr X Si Y] N ( provided that both atomic ratio, X is 0.03 to 0.30, Y represents a 0.01-0.05) satisfies A composite nitride layer of Ti, Cr and Si;
(C) The upper layer of the hard coating layer is formed by vapor deposition on the surface of the lower layer, and each has an alternately laminated structure of thin layers A and B each having an average layer thickness of 0.01 to 0.3 μm. And
The thin layer A is

_{Formula: [Ti 1-X-Y} Cr X Si Y] N ( provided that, X, Y are both atomic ratio, X is 0.03 to 0.30, Y is a 0.01-0.05 Ti, Cr and Si composite nitride layer satisfying

The thin layer B is a Ti nitride (TiN) layer,
A surface-coated cubic boron nitride-based ultrahigh pressure sintered material cutting tool that exhibits excellent chipping resistance in high-speed intermittent cutting of high-hardness steel with a hard coating layer made of

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